There are four valves in the heart that serve to direct the flow of blood through the two sides of the heart in a forward direction. On the left side, the mitral and aortic valves direct oxygenated blood coming from the lungs, through the left side of the heart, into the aorta for distribution to the body. On the right side, the tricuspid valve, located between the right atrium and the right ventricle, and the pulmonary valve, located between the right ventricle and the pulmonary artery, direct de-oxygenated blood coming from the body, through the right side of the heart, into the pulmonary artery for distribution to the lungs. The anatomy of the heart and the structure and terminology of heart valves are described and illustrated in detail in numerous reference works on anatomy and cardiac surgery, including standard texts such as Surgery of the Chest (Sabiston and Spencer, eds., Saunders Publ., Philadelphia) and Cardiac Surgery by Kirklin and Barrett-Boyes, Pathology and Abnormalities of Heart Valves, incorporated herein by reference.
All four heart valves are passive structures in that they do not themselves expend any energy and do not perform any active contractile function. They consist of moveable "leaflets" that are designed simply to open and close in response to differential pressures on either side of the valve. The mitral valve has two leaflets and the triscupid valve has three. The aortic and pulmonary valves are referred to as "semilunar valves" because of the unique appearance of their leaflets, which are most aptly termed "cusps" and are shaped somewhat like a half-moon. The components of the mitral valve assembly include the mitral valve annulus; the anterior leaflet; the posterior leaflet; two papillary muscles which are attached at their bases to the interior surface of the left ventricular wall; and multiple chordae tendineae, which couple the mitral valve leaflets to the papillary muscles.
The problems that can develop with valves can be classified into two categories: (1) stenosis, in which a valve does not open properly, or (2) insufficiency, or regurgitation, in which a valve does not close properly.
Mitral regurgitation ("MR") is caused by dysfunction of the mitral subvalvular apparatus or direct injury to the valve leaflets. Multiple etiologies can lead to mitral regurgitation, with myxomatous degeneration of the valve and ischemic heart disease accounting for close to 60% of cases. Repair of the diseased valve requires major surgery on cardiopulmonary bypass to allow access to the valve. Consequently, some patients in the early or late stages of the disease are not considered appropriate candidates due to the high risk associated with the operation. Multiple studies have demonstrated that prosthetic replacement of the mitral valve can lead to significant postoperative left ventricular dysfunction and often requires lifelong treatment with anticoagulants. Mitral valve repair, using a posterior annuloplasty ring, has demonstrated improved results with better ventricular recovery. Nevertheless, recent studies performed by the inventors (Umana et al., Surg Forum 1997) have revealed that posterior ring annuloplasty causes changes in ventricular geometry that lead to paradoxical movement of the normal papillary muscles, further deteriorating ventricular performance. In contrast, the "bow-tie" repair in which the anterior and posterior leaflets of the mitral valve are fixed in opposition appears to enhance annular contractility while preserving ventricular architecture. This has resulted in improved postoperative ventricular function almost uniformly.
The present invention addresses the needs of all patients with mitral regurgitation without mitral stenosis, including those who heretofore may have been excluded due to having only moderate MR or being too sick to be candidates for major surgery.
The present invention finds utility not only for the repair of mitral valves but for all valves of the circulatory system, including aortic valves, tricuspid valves, and venous valves.
Techniques for improving the efficacy of corporeal valves are known. For example, Laufer et al., U.S. Pat. No. 5,609,598 describes a valving system for treatment of chronic venous insufficiency. The system has inherent limitations in terms of its effectiveness for the procedure described and its applicability, if any, to other valves, especially cardiac valves.